Need to stop sprinkler system from siphoning from water treatment

[sp00kster]

I am not sure if this is proper forum but any help greatly appreciated - Quick version

We are on a well - sprinkler system is the first plumbed outlet after pressure tank then on to water treatment system (chlorination). Problem I am having is that the sprinkler system when on is siphoning from the water treatment system. Basically watering the yard with heavily treated water. I installed a spring type double check valve as well as a pressure gauge for monitoring and regardless my efforts it still continues to siphon through the check valve especially on high volume stations. All fittings are brass 1" NPT.

I was looking at perhaps back flow preventers (guessing) - but there are many styles and do not wish to purchase wrong valve

Any help in this matter would be greatly appreciated

[dubldare]

First, make sure you have a pressure vacuum breaker installed where the irrigation feed leaves the house, prior to the connection to the sprinkler system. The critical-level (CL) of the vacuum breaker must be at least 12" above the highest point of irrigation piping. If this cannot be done (due to elevation), an RPZ is required. This protects your drinking water.

Secondly, a DCIAV (double check, intermediate atmospheric vent) style vacuum breaker would prevent the water on the house side of the system from migrating back to the irrigation system. An RPZ could also be used. Both the RPZ and the DCIAV provide an atmospheric break in the piping, meaning there is virtually no possibility for back siphonage.

Your problem sounds to be as one of inadequate supply for everything you are trying to do. I would surely hope you don't have a pump for the irrigation system, as that would explain a lot. Perhaps reducing the size of your zones (adding more, making each zone 'smaller') is your best bet. You most likely are exceding the flow rate of your well vs demand on your larger zones. Please don't ignore this part, as it is most likely the crux of your issue.

With all the examples above, and what you've already done, your system is 'closed' and requires a thermal expansion tank for your water heater. Make sure you have one.

[Terry]

I like to use a double check valve for irrigation backflow.

Series: 007
Description: Double Check Valve Assemblies
Size Range: 1/2 to 3 in. (15 to 80mm)

Series 007 Double Check Valve Assemblies prevent the backflow of contaminated water into the potable water supply. It consists of a bronze (1/2 to 2 in) or fused epoxy coated cast iron (2 1/2 to 3 in) body construction that is easy to maintain and service. Series 007 is ideal at referenced cross-connections identified as non-health hazard applications. Check with local inspection authorities for installation requirements. Maximum Working Pressure: 175psi (12.06 bar).

http://www.wattsreg.com/

[Gary Swart]

You're thinking right about the backflow preventer. These are required on public water supply systems. Basically what you do is tee the main supply line to feed untreated water through a backflow preventer for the irrigation and the other side of the tee into the treatment device. This will do two thing for you. You will not be irrigating with the treated water, and you will not be syphoning water from the irrigation side into you household supply. I don't remember the brand of backflow I use, but any decent plumbing supply should be able to provide a suitable one. In my city, I am required to have an annual inspection to verify the backflow is still performing properly. You won't have the legal requirement that I do, but I'd suggest you find a plumber that can test yours for you own safety. I pay $25 for my inspections.

[dubldare]

If I'm reading him right, he is siphoning water from the treatment system (house water) into the irrigation system. Any backflow device solely on the irrigation branch will not stop that.

[Cass]

A Watts #7 check valve installed between the hose bib / sprinkler and treatment system with the flow direction towards the treatment system will solve the problem. The sprinkler should have a backflow on it also.

[Gary Swart]

I stand corrected, Dubldare is correct. I misread the question. I wonder if a double check valve in the potable line might be the answer. In other words, a double check valve in both lines. This is a guess, I'd sure check deeper into this before investing in the valve, but it seem logical that it would work.

[sp00kster]

Thanks for all the responses - Guess I am still am a bit confused by posts. I will recap a bit to explain.

1st - water supply enters through basement wall into pressure tank
2nd - T's off immediatly (sprinkler - potable house water treatment system)
3rd - sprinkler system already has an anti-siphon valve outside to prevent potable water contamination
4th - Potable house water treatment side already has a Watts (Series: 7) dual check valve installed immediatly after T - to prevent potable treated water from siphoning into the sprinkler system.
5th - Between our well service, sprinkler service and water treatment service (all of which are pointing fingers at each other)

Guess what is confusing me is what is the difference in a back-flow prevention valve and dual-check / double check valve. If / when you go to Watts url (www.wattsreg.com) all are labled "back flow prevention valves". For the life of me I do not understand how when the sprinkler system is on it is able to siphon the potable house water back through this dual check valve (replaced twice), in the first place. Must be some serious negative pressure or something. I have no problem purchasing what ever it will take to stop this backflow just that I know from experience that it will take more than a Watts (Series: 7) dual check valve / back flow preventer.

[Cass]

How do you know it is backflowing/siphoning?

[sp00kster]

All of this was brought to my attention in the first place when we noticed that chlorinator was using an extremely large amount of chemical during the watering season. So we called our water treatment service company out and they are the ones that realized that the chlorinator was running while the sprinklers were running (due that chlorinator was wired into the well pressure switch (creating a very concentrated solution in the retention tank)). At the time there was not even the thought of it siphoning out to the sprinklers just that the chlorinator was running regardless whether it be potable water or sprinkler. So they sent plumber out who installed a single check valve, pressure gauge and a independant pressure switch on the potable water side. So I am told that now the chlorinator will only come on when potable water side pressure drops thus tripping the indepandant pressure switch and allowing the chlorinator to run with pump. He showed us by engaging the sprinkler system and the house pressure did not drop and the chlorinator did not come on. Later we found that it did work on zones 1 - 3 that were very low volume (pop-ups and drip) - until the high volume zones 4 - 7. As soon as any of these zones would engage the potable water pressure side would quickly drop and the chlorinator again would engage. I also used our water test kit to test for chlorine via the sprinkler system on zone 4 (5ppm).

I called our water treatment service company back out and they in turn sent plumber back out - he in turn replaced check valve with dual check valve. I was not home to test while he was here (still did not work). Now they are all saying that is best they can do. Now makes me wonder if he really was a plumber in the first place.

Any way you have now heard the long version and any help would be greatly appreciated

[Cass]

I am wondering if

#1 the chlorine is affecting the check valve some how.

#2 if there is a cross connection somewhere that you don't know about.

[sp00kster]

Chlorine can only get to the valve in the first place because of siphoning. I have attempted to create a diagram in Microsoft Word as an illustration - I will attempt to attach.

[Gary Swart]

The only thing I can think of is that the check valve is not functioning. The backflow I use is exactly the one Terry pictured earlier, and should do the job. I would have it tested to make certain it is functioning properly. They can fail, that's why my city requires an annual test.

[sp00kster]

Ok - Will replace again - a big thanks to all of you for your input. Ever need any advice on replacement windows or doors feel free to give me a shout and perhaps I can return the favor!!!

Best Regards

[Gary Swart]

NOTE: I was only suggesting you have it checked. While this seems to me to be the only logical possibility of the cause of your problem, I'm sure as heck no expert! Any irrigation supply company should be able to test the backflow valve. If it's working OK, then I'm stumped.